RIF1 coordinates the stepwise post-replicative H3K9me3 recovery.

DNA replication dilutes parental histones and their post-translational modifications, requiring restoration of epigenetic marks on newly incorporated histones. H3K9me3 restoration is unusually slow, extending into the following G1 phase, but the mechanisms governing this delay remain unclear. Here, we show that RIF1 reassociation with heterochromatin during mitotic exit establishes a permissive chromatin environment for histone methyltransferases to resume H3K9me3 deposition. RIF1 promotes recruitment of SUV39H1 and HP1α/β and the increase of H3K9 tri-methylation during G1. RIF1 also recruits protein phosphatase 1α (PP1α) to heterochromatin, and RIF1-PP1α interaction is essential for the maintenance of H3K9me3 levels. Moreover, RIF1-PP1 complex temporally restrains the activity of Aurora kinase at heterochromatin, preventing premature H3S10 phosphorylation before replication and creating a permissive time-window for SUV39H-mediated reinstatement of H3K9me3.